Fluorescent lighting is widely used in residential and commercial applications. Because a fluorescent lamp consumes only one-third of the power that is dissipated in an incandescent lamp of equivalent light output, and its lifetime is 1000 times that of an incandescent lamp [1], it conserves energy and reduces the energy cost of lighting.
The development of compact fluorescent lamps (CFLs) has increased the use of fluorescent lighting in residential applications. The key component of a CFL is the high frequency electronic ballast that provides proper lamp ignition and lamp current stabilization. It is known that high frequency electronic ballasts operating at >25 kHz provide more desirable performance than magnetic ballasts in fluorescent lamps, as they: (1) reduce the ballast volume; (2) increase efficiency by at least 20%; (3) eliminate light flickering; (4) implement advanced dimming control with great flexibility. However, like other electronic appliances, the harmonics of the line current from the fluorescent lamp must comply with the IEC 1000-3-2 standard [2] when the lamp power exceeds 25 W.
In a conventional electronic ballast as shown in FIG. 1A, a diode rectifier connected across a DC-link capacitor with a resonant inverter produces a poor power factor (e.g., less than 0.6), and the harmonics content of the line current exceed the limits of the standard. A simple way to correct the power factor problem is to insert a power factor correction (PFC) circuit between the rectifier and the inverter as shown in FIG. 1B so that the shape of the line current follows the sinusoidal line voltage and a high power factor can be achieved at the input. However, this kind of circuit configuration usually results in a high cost. Moreover, the large size of the circuit is incompatible with the size of a CFL.
Currently-available technology cannot achieve low cost, small size, high power factor, and dimmability in fluorescent lamps. In particular, dimming and power factor have generally been sacrificed in consumer grade lamps in favour of low cost and small size.